1) We need to merge trees with the same priority in order
to catch case when we have package with different versions in
repos with the same priority, eg:
repo2, priority=10, package=foo-5.3
repo1, priority=5, package=asd-1.2
repo3, priority=10, package=foo-7.1
--> sort(key=priority) can result:
repo1, priority=5, package=asd-1.2
repo2, priority=10, package=foo-5.3
repo3, priority=10, package=foo-7.1
so we will return: foo-5.3 instead we must return foo-7.1
2) priority must be a mandatory parameter for Repository
3) Align rpm default priority _DEFAULT_PRIORITY: N, where
N is an integer from 1 to 99. The default priority for
repositories is 99. The repositories with the lowest
numerical priority number have the highest priority.
Closes-bug: #1590525
Change-Id: I8299b1502775cc68bd1c783487ce7dc802a31a05
e1f7a5975a